The present invention relates to skate wheels, more specifically, the present invention relates to the construction of a skate wheel for devices such as roller skates and skateboards.
Roller skates of various types are well known in the art. The wheels for skates used in outdoor skating have often been constructed of metal, and the wheels of indoor skates have typically been constructed of wood. For recreational activity, skaters often skate on boardwalks, sidewalks, and streets, the surfaces of which may be uneven and bumpy. More experienced skaters may also become involved in sports, such as roller hockey, that require skating with greater precision and speed.
In order to enhance the safe performance of roller skates while maintaining the precision and speed desired, skates have been equipped with polyurethane wheels that are capable of maintaining good traction while the skate is in motion. For example, Peterson et al. U.S. Pat. No. 5,641,365 teaches a skate wheel that has a hard polyurethane hub with a soft polyurethane wheel body.
A drawback associated with these soft wheels is an increase in the amount of rolling resistance. More effort must be expended by the skater to overcome the increased rolling friction, which causes a relative loss of performance, particularly on straightaways. Another disadvantage with softer wheels is their tendency to wear out quickly. Attempts to create a harder wheel have been made, such as in Boyer et al. U.S. Pat. Nos. 5,725,284 and 6,036,278. These patents teach a skate wheel with a nylon hub, a relatively soft polyurethane core and a somewhat harder polyurethane outer body. A problem associated with such a wheel is that the harder outer body compresses against the softer inner body of the wheel and results in a significant distortion in the shape of the wheel and a temporary out of round condition. It will be appreciated that this compression may adversely affect the stability and performance of the skate.
Thus, there is a need in the art for a skate wheel that will facilitate precision and speed, while maintaining a controlled, smooth ride for the skater.
The present invention meets that need with a skate wheel that provides a smooth ride for the skater, while maintaining good precision and speed. The skate wheel comprises an outer polymeric layer, an inner polymeric layer having a hardness which is less than the hardness of the outer polymeric layer, and an intermediate layer, separating the outer and inner layers. The skate wheel may further include a central hub that is preferably comprised of aluminum. The central hub may be recessed on one side of the inner polymeric layer. The central hub can be flush with the inner polymeric layer, the intermediate layer, and the outer polymeric layer on both sides of the wheel. Typically, the inner and outer polymeric layers comprise polyurethane. Preferably, the inner layer has a Shore A hardness of about 45 to 75. Preferably, the outer layer has a Shore A hardness of about 80 to 95. The intermediate layer typically comprises plastic or metal, wherein the preferred metal is aluminum. The intermediate layer is preferably relatively rigid. The skate wheel may include an illumination device that is typically positioned in the inner layer. Preferably, the outer polymeric layer, the inner polymeric layer, and the intermediate layer are concentric annular layers surrounding a central hub.
The skate wheel of the present invention comprises a generally annular central hub, an inner generally annular polymeric layer surrounding the central hub, a generally annular intermediate layer surrounding the inner polymeric layer, and an outer generally annular layer surrounding the intermediate layer. The outer layer has a hardness which is greater than the hardness of the inner polymeric layer. The generally annular central hub can be recessed on one side. The generally annular central hub may be flush with the generally annular inner polymeric layer, the generally outer polymeric layer, and the generally annular intermediate layer. Typically, the generally annular intermediate layer comprises plastic or metal. The preferred metal for the generally annular intermediate layer is aluminum. The generally annular intermediate layer may be relatively rigid. An illumination device may be positioned in said generally annular inner polymeric layer.
Accordingly, it is a feature of the invention to provide a skate wheel where the hard outer polymeric layer does not compress directly against and distort the shape of the softer inner polymeric layer. This provides a smoother ride for the skater while maintaining good precision and speed. Other variations in the invention will become clear in light of the description below.